REVIEW Open Access
The expanding role of aerosols in systemic drug delivery, gene
therapy and vaccination: an update Beth L Laube
Abstract
Until the late 1990s, aerosol therapy consisted of beta2-adrenergic
agonists, anti-cholinergics, steroidal and non-steroidal agents,
mucolytics and antibiotics that were used to treat patients with
asthma, COPD and cystic fibrosis. Since then, inhalation therapy
has matured to include drugs that: (1) are designed to treat
diseases outside the lung and whose target is the systemic
circulation (systemic drug delivery); (2) deliver nucleic acids
that lead to permanent expression of a gene construct, or protein
coding sequence, in a population of cells (gene therapy); and (3)
provide needle-free immunization against disease (aerosolized
vaccination). During the evolution of these advanced applications,
it was also necessary to develop new devices that provided
increased dosing efficiency and less loss during delivery. This
review will present an update on the success of each of these new
applications and their devices. The early promise of aerosolized
systemic drug delivery and its outlook for future success will be
highlighted. In addition, the challenges to aerosolized gene
therapy and the need for appropriate gene vectors will be
discussed. Finally, progress in the development of aerosolized
vaccination will be presented. The continued expansion of the role
of aerosol therapy in the future will depend on: (1) improving the
bioavailability of systemically delivered drugs; (2) developing
gene therapy vectors that can efficiently penetrate the mucus
barrier and cell membrane, navigate the cell cytoplasm and
efficiently transfer DNA material to the cell nucleus; (3)
improving delivery of gene vectors and vaccines to infants; and (4)
developing formulations that are safe for acute and chronic
administrations.
Keywords: Systemic drug delivery by inhalation; Aerosolized gene
therapy; Vaccination by inhalation
Introduction There are many advantages to administering medications
to the lung as an aerosol. These include: a more rapid onset of
action for short-acting bronchodilators, compared to oral therapy;
high local concentration by delivery dir- ectly to the airways;
needle-free systemic delivery of drugs with poor oral
bioavailability; and pain- and needle-free delivery for drugs that
require subcutaneous or intraven- ous injection. Traditional
aerosol therapies with the lung as the target consist of
short-acting β2-adrenergic agonists and long-acting β2−adrenergic
agonists (LABA), anticho- linergics, inhaled corticosteroids
(ICSs), nonsteroidal anti- inflammatories, antibiotics and
mucolytics. Devices that are available to deliver these drugs
include pressurized
Correspondence:
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Institutions, Suite 3015, The David M. Rubenstein Building, 200
North Wolfe Street, Baltimore, MD 21287, USA
© 2014 Laube; licensee Springer. This is an Ope Attribution License
(http://creativecommons.or in any medium, provided the original
work is p
metered-dose inhalers (pMDIs), used either alone, or attached to
spacers, or valved holding chambers (VHCs), breathactuated
(BA)-pMDIs, dry powder inhalers (DPIs), jet nebulizers, vibrating
mesh nebulizers and soft mist inhalers. Well-established treatment
guidelines for the management of asthma [1] and chronic obstructive
pul- monary disease (COPD) [2] each recommend inhaled therapy as
the primary route to administer these medica- tions. Treatment
guidelines for cystic fibrosis (CF) also include recommendations
for inhalation of aerosolized medications [3,4]. Guidelines for
inhalation therapy to treat these diseases will not be covered in
this review. A comprehensive presentation of old and newly-approved
devices and their correct use in treating these diseases has also
been published [5] and will not be included in this review. This
review will focus on the newest applications for aerosol therapy by
oral inhalation. When possible,
n Access article distributed under the terms of the Creative
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results from clinical studies, rather than preclinical stud- ies,
will be highlighted and delivery devices will be included if they
are a new design and critical to the suc- cess of the application.
Updates on new applications for intranasal therapy are beyond the
scope of this review and can be found in several referenced
articles [6-14]. New applications for oral inhalation now include
drugs
that: (1) target the systemic circulation as a means to treat
disorders unrelated to the lung (systemic drug delivery by
inhalation); (2) deliver nucleic acids that lead to perman- ent
expression of a gene construct, or protein coding sequence, in a
population of cells within the lung, thereby reversing or
preventing a disease process (aerosolized gene therapy); and (3)
provide needle-free immunization and prevention against infectious
diseases (vaccination by in- halation). Since first reviewing this
subject in 2005 [15], each of these new applications has met with
varying degrees of success in terms of achieving clinical efficacy
and commercialization. This brief review provides an up- date on
the status and challenges facing each of these new applications and
focuses on an example that is furthest along in development and/or
affects the most people. Within each example are success stories,
failures and les- sons to be learned. Addressing those lessons will
enhance these applications in the future.
Review Systemic drug delivery by inhalation Because of the many
advantages to aerosol therapy men- tioned above, a number of
systemically active drugs have been developed as possible
candidates for aerosol deliv- ery through the lung into the
systemic circulation. For these drugs, it is important that
delivery lead to adequate systemic absorption with no irritability,
or damage, to the airways or alveoli. Drugs that have been tested
include opioids for pre- and post-operative analgesia,
dihydroergotamine (DHE) for acute treatment of migraine, interferon
β to treat multiple sclerosis, leuprolide acetate to treat
prostatic cancer, infertility and post-menopausal breast cancer,
calcitonin to treat postmenopausal osteopor- osis, growth hormone
releasing factor to treat pituitary dwarfism and insulin to treat
diabetes. A few of these drugs have shown promise in human
trials and some have been commercialized. Opioids such as morphine
and fentanyl have been tested as a liquid aerosol generated by
traditional jet nebulizers [16] and by the AERx® vibrating mesh
prototype nebulizer [17]. The usefulness of inhaled opioids lies in
the elimination of an intravenous catheter with the potential of
providing rapid-onset, patient-controlled analgesia. A large
variabil- ity in absorption was reported with jet nebulizer
adminis- tration [16], which likely will limit acceptance as a
method for pre- or post-operative pain control with these devices.
Pain management was more predictable with the
AERx® device (Aradigm Corp., Hayward, CA, USA) [17]. Another pain
management drug, DHE, has proven super- ior to placebo for the
acute treatment of migraine in a phase 3, double-blinded,
multicenter study [18]. In that study, a novel formulation of DHE
(LEVADEX™, MAP Pharmaceuticals, Mountain View, CA, USA) was
delivered to the systemic circulation using the TEMPO® pMDI (MAP
Pharmaceuticals). Calcitonin has been successfully delivered to the
systemic circulation intranasally [7,8] and is now available as
Miacalcin® (Novartis Pharmaceuticals Corp, East Hanover, NJ, USA)
nasal spray to treat post- menopausal osteoporosis in females
greater than 5 years post menopause.
Best example of systemic drug delivery by aerosolization: treating
diabetes with oral inhalation of insulin Although there are several
other successful drugs that have been administered to the systemic
circulation by inhalation, the best example of the expanding role
of aerosol therapy into systemic drug delivery is treating diabetes
with oral inhalation of insulin. This is because this route of
administration has the potential to eliminate subcutaneous (SC)
injection of insulin for a significantly large patient population.
An estimated 370 million people worldwide have diabetes [19] and
the majority of these have non-insulin dependent diabetes mellitus
(NIDDM), or type-2 diabetes. The goal for the treatment of type-2
diabetes is to maintain glucose control in the normal range to
prevent long-term complications. Typically, the first line of
treatment is oral anti-diabetic medications. Eventually,
anti-diabetic medications fail and type-2 patients need to
administer insulin SC four times/day (i.e. before meals and at
bedtime) to achieve good con- trol. Because injection hurts,
compliance with treatment is often reduced. More importantly,
patients who would benefit from early intervention with insulin
treatment decline treatment because of the pain and inconvenience
associated with injection. A second reason why treating diabetes
with oral inhal-
ation of insulin is the best example of the expanding role of
aerosol therapy into systemic drug delivery is because what we now
know about systemic drug delivery of pep- tides by inhalation was
learned during the development of inhaled insulin and the study of
its success and early failure continues to inform future
development of sys- temic drug delivery by inhalation, as well as
other new applications of aerosol therapy. The notion that insulin
could be administered through
the lung to the systemic circulation by inhalation was investigated
in the 1970s [20,21]. From those early trials, several challenges
were identified that needed to be over- come. These included: (1)
determining the appropriate lung target; (2) determining the
inhaled dose that con- trols blood glucose levels; and (3)
developing new devices
Figure 1 The AFREZZA® (MannKind Corporation, Valencia, CA, USA): a
second generation device for delivering dry powder insulin. It is a
drug-device combination product, consisting of AFREZZA inhalation
powder pre-metered into single use dose cartridges and a
lightweight, AFREZZA inhaler. Insulin is placed into the chamber in
an aspirin-like tablet. Closing the device crushes it into a fine
powder which is then inhaled by the patient (downloaded from
MannKind website at
http://www.mannkindcorp.com/product-pipeline-diabetes-afrezza.htm).
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that deliver the dose to the target. By the early 1990’s, several
pharmaceutical companies and device manufac- turers began to
address these challenges. Work in ani- mals showed that the
appropriate target for aerosolized insulin and other drugs
delivered through the lung for systemic administration is the
alveolar region [22]. This is because the alveolar region comprises
a resorptive sur- face of 50-75 m2, which provides a surface area
for drug absorption that is the size of a tennis court. In
addition, mucociliary clearance is minimal in the alveolar region.
Once drug deposits in the alveolar region, the residence time is
long, enhancing the probability of absorption. Finally, the cell
barrier to absorption is extremely thin (0.1 mm) in the alveolar
region, thereby enhancing the possibility for absorption from the
epithelial layer to the lung vasculature. By the late 1990s,
results from several studies [23-26]
showed that a dose of 1.0 U/kg body weight human regu- lar insulin
aerosol controlled fasting glucose levels and a dose of 1.5 U/kg
body weight controlled postprandial glu- cose levels. However, this
dose posed an early limitation to this route of administration,
since it was approximately 10 times the dose given subcutaneously
(i.e. ~0.1 U/kg body weight). Nevertheless, the Exubera® Pulmonary
Insulin Delivery
System (Pfizer Pharmaceuticals, New York, NY; and Nektar
Therapeutics, San Carlos, CA), was approved by the U.S. Food and
Drug Administration in 2006 for use in adults with both type 1 and
type 2 diabetes and became commercially available soon thereafter
[27,28]. By early 2007, two additional devices and formulations
were in Phase III testing. These included the AERx® Insulin
Diabetes Management System (Novo-Nordisk A/S, Bagsverd, Denmark;
and Aradigm Corp., Hayward, CA) and the AIR® Inhaled Insulin System
(Eli Lilly and Co., Indianapolis, IN; and Alkermes Inc., Cambridge,
MA) [29-31]. However, between October, 2007 and May, 2008,
production of all three products had been discontinued.
What went wrong?
1. The cost of inhaled insulin was higher than injectable insulin.
One analysis demonstrated that Exubera®’s inhaled insulin cost
about $5 per day, compared to $2-3 per day by injection [32]. The
higher cost was due in part to the lower bioavailability of
Exubera® inhaled insulin compared to SC. The bioavailability of
Exubera was only 10-15% of the SC dose [26].
2. Safety became an issue. Studies with Exubera® that lasted 6
months, showed increased insulin binding antibodies, coughing and a
reduction in diffusing capacity, compared to injected insulin
[33].
However, longer-term studies showed that reductions in lung
function parameters were small, non-progressive and reversible with
discontinuation of treatment [33].
3. Sales in the U.S. of Exubera® were lower than expected, perhaps
because of the cost, or safety issues, or because few patients, or
care givers, realized the advantages of this route of
administration compared to injection therapy.
Second generation delivery system for inhaled insulin AFREZZA® is a
pocket-size device developed by MannKind Corporation (Valencia, CA,
USA) (Figure 1) [34]. It is a second generation delivery system for
inhaled insulin with several advantages over earlier generations.
First, it delivers microparticles (Technospheres™) of insulin.
Technosphere™ insulin particles (human regular insulin loaded onto
a fumaryl diketopiperazine molecule) are optimized for deposition
in the alveolar region of the lung. Greater than 90% of the
particles are in the respirable range, with a mean particle
diameter of 2.5 μm [35]. Bioavailability of this new formulation is
also estimated to be 24-28% of SC [36] which is higher than for
human regular insulin delivered by the Exubera® device. Unlike the
Exubera®, it is small and portable and appears to be easier to use.
In a recent clinical trial, the change in HBA1C for 211 type 2
patients after 52 weeks on prandial inhaled Technosphere plus
bedtime insulin glargine was similar and non-inferior to that of
237 patients who were injected twice daily with biaspart insulin
(70% insulin aspart protamine suspension and 30% insulin aspart)
(Figure 2A and 2B) [36]. In addition, weight gain was lower and
hypoglycemic events were fewer on
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Technoshpere compared to patients on injected insulin. Thirty-two
percent of patients treated with Technosphere reported cough
compared to 14% of patients treated with injected insulin. Most
cough events occurred during the first 10 minutes of inhalation and
declined to about 2/week by week 6. There were no differences
between treatment groups in terms of pulmonary function changes. A
recent review based on a MEDLINE search of studies relevant to
Technosphere insulin concludes that it is has a pharmaco- kinetic
profile suitable to meet prandial insulin needs in patients with
diabetes [37]. The company is awaiting FDA approval for mealtime
glucose control only. If approved, it could lead to earlier
treatment of diabetes with insulin for patients who have resisted
such treatment due to fear of, or pain associated with, injection
therapy.
Future directions To insure satisfactory outcomes and patient
acceptability of systemic drug delivery by aerosolization in the
future, it is clear that the bioavailability of expensive drugs
like insulin with relatively low bioavailability needs to be
improved. Sug- gestions for improving bioavailability include:
better target- ing of the alveolar region with nanoparticle
(<0.1 μm in diameter) formulations, or formulations containing
porous particles that have aerodynamic characteristics similar to
extrafine particles (~1.0 μm in diameter); and enhancing ab-
sorption by adding absorption enhancers that do not dam- age lung
tissue. Several additives that have been tested in rats appear to
enhance absorption and permeation and may be appropriate to improve
absorption in future pulmonary protein formulations. These include
endogenous surfactants such as DPPC [38,39], citric acid [40], and
hydroxypropyl- cellulose [41]. It is also clear that: (1)
formulations are needed that
do not produce cough, or changes in lung function, and
are safe for acute and chronic administrations; (2) the device
should be small, portable and easy to use; (3) the total cost of
the device and formulation should be simi- lar in cost to the
injection product; and (4) patients and physicians should be
well-educated in terms of the advantages of this route of a
dministration compared to injection therapy to ensure
compliance.
Aerosolized gene therapy The lung is an important target organ for
gene therapy. This is because there are a number of lung diseases
that could benefit from this type of treatment. These include: lung
cancer, asthma, cystic fibrosis and alpha-1-antitrypsin deficiency.
The goal of aerosolized gene therapy is to cor- rect the lung
disorder with delivery of a functional copy of the aberrant gene to
the appropriate target within the lung.
Viral vectors versus non-viral vectors for gene therapy As with
systemic drug delivery by aerosolization, aerosolized gene therapy
will likely require repeat dos- ing. In order to avoid lung damage
as a result of repeat therapy, it is important that the vector that
is selected to deliver the functional genetic material does not
cause immune responses from the host, or lead to mutagenesis over
time. Although there are a number of viral and non-viral vectors
that are available for aerosoliza- tion that can deliver the
functional genetic material, the identification of safe vectors has
been one of the major challenges to the development of aerosolized
gene therapy [42,43]. Viral vectors include retroviruses,
lentiviruses, adenoviruses (Ad) and adeno-associated viruses (AAV).
Retroviruses are capable of long-term gene expression following
genomic integration but only in non-dividing cells, whereas,
lentiviruses are capable of long-term gene
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expression in both non-dividing and dividing cells. How- ever, both
types of viruses present a high risk of insertional mutation
leading to oncogenesis. Adenoviruses infect non- replicating cells,
show potential for persistent expression and present low risk of
insertional mutagenesis. However, they can trigger a strong immune
response by the host. Unlike adenoviruses, AAV do not trigger a
strong immune response by the host, but they have a small packaging
capability (~4.7 kb), so they are limited in the amount of genetic
material they can carry, and they have reduced efficacy with
repeat-administration. Non-viral vectors are carrier molecules that
are either
cationic lipids, or cationic polymers, that bind to nega- tively
charged plasmid DNA and either encapsulate or condense the DNA to
generate lipoplexes and polyplexes. Non-viral vectors are generally
less efficient than viral vectors because they lack specific
components that could help with endosomal escape, movement through
the cytoplasm and nuclear uptake. The simpler composition of
non-viral vectors, however, may have an advantage over viral
vectors, since they are free of non-human com- ponents, making
re-administration potentially more suc- cessful [44,45]. Of the
vectors available for delivering genetic material
for gene therapy, AAV vectors have been the most uti- lized in
terms of animal experiments and clinical trials. Currently, the
most common carrier is the viral vector AAV2, but recent studies
suggest that AAV2 with capsids from serotypes 1, 5 and 6 may be
more efficient in trans- ducing airway epithelial cells than AAV2
[46,47]. Some progress has been made in improving non-viral gene
transfer [48], but more safety data is needed before they can be
safely administered to humans on a chronic basis. There are
currently no dry-powder, or metered-dose inhaler formulations for
any vector-drug combination. Therefore, the field is further
limited by delivery in a liquid formulation using a
nebulizer.
Best example of aerosolized gene therapy: treating cystic fibrosis
(CF) Development of aerosolized gene therapy for lung cancer and
alpha-1-antitrypsin deficiency has not progressed be- yond the
preclinical stage. Results from clinical trials with early
therapies have not shown efficacy. On the other hand, aerosolized
gene therapy for treating cystic fibrosis has had some success in
clinical trials and details of those efforts are reported here.
Approximately 70,000 people worldwide have cystic fibrosis (CF), an
inherited, autosomal recessive disease. Mutations in the cystic fi-
brosis transmembrane conductance regulator (CFTR) gene lead to loss
of chloride, sodium and water transport, impaired mucus removal,
obstructed airways, chronic infection and end stage lung disease.
The goal of aerosolized gene therapy in treating cystic fibrosis is
to
restore CFTR function and normal chloride channel function in the
lungs. Over the years, there have been a number of challenges
to aerosol delivery of vectors carrying intact CFTR com- plementary
DNA (cDNA). First, there has been the challenge of delivering an
adequate dose to infants, who are an important target population.
This is because identi- fication of infants who are afflicted with
CF is now pos- sible at birth and early gene therapy holds the
promise of correcting the abnormality before irreversible lung dam-
age can occur. However, due to anatomic, physiologic and behavioral
factors, delivery of aerosols to infants is chal- lenging and
highly variable. Gene transfer therapy is likely to be extremely
expensive, so improving delivery efficiency and reducing
variability of delivery to small children will result in less waste
and help insure the desired effect. Another challenge has been
uniform delivery of the drug
vector to the lungs of adult patients with CF. Disease in adults
with CF is significantly more severe, compared to children with CF
(Figure 3) [49]. Increased disease severity is shown by a lower
percent forced expiratory volume in one second (FEV1) in adults,
compared to children. Increased severity in disease leads to uneven
distribution of the drug vector, with areas of the lung that are
unob- structed receiving a higher dose of vector than regions that
are partially, or fully obstructed (Figure 4). Such uneven
distribution of the drug vector could make treatment less
efficacious. These same challenges are likely to apply to treating
infants, or adults with obstructed airways, with aerosolized gene
vectors for other lung diseases. Additional challenges to
aerosolized gene therapy for
CF that likely apply to aerosolized gene therapy for other lung
diseases include delivery of DNA through the mucus barrier. The
mucus barrier is thick and viscous in patients with CF, and in
patients with chronic obstructive lung disease (COPD), there is
excess mucus production. Gene vectors whose target is the airway
epithelial cell must be able to penetrate beyond the mucus barrier
to reach their cell target. Another challenge is the need for
vectors that recognize receptors on the apical surface of airway
epithelial cells. Many vectors only recognize receptors on the
basal-lateral surfaces, which are very difficult to access. The
gene vector must deliver DNA to the cell nucleus. To do this, the
vector must penetrate the cytoplasmic membrane, overcome
cytoplasmic prote- ases and penetrate the nuclear membrane. To
date, 24 clinical trials with aerosolized gene vectors
have been carried out since the cloning of the CF gene in 1989.
Nine Ad CF gene therapy trials were carried out in the upper and
lower airways of CF patients between 1993 and 2001 [50]. These
trials showed that low level gene transfer can be achieved in some
patients, but administra- tion resulted in lung inflammation and
induced humoral and cellular immune responses, affecting the
efficacy of
Figure 3 Percent of people with cystic fibrosis by age with
normal/mild forced expiratory volume in one second (FEV1), moderate
FEV1 and severe FEV1. The majority of children have FEV1 values in
the normal to mild range, indicating mild disease and mild airway
obstruction. Adults age 18–29 and 30+ have FEV1 values in the
moderate to severe range, indicating severe disease and increased
airway obstruction (downloaded from Cystic Fibrosis Foundation
website at
http://www.cff.org/UploadedFiles/Research/ClinicalResearch/2011-Patient-Registry.pdf).
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re-administration. These shortcomings have not been overcome [48].
Between 1999 and 2007, six clinical trials were carried
out with the AAV2 serotype [51]. Acute administration appeared to
be safe, but assessment of the efficiency of vector-specific
expression was lacking and in another large trial there was no
improvement in lung function [52]. Moreover, repeat dosing with the
AAV2 serotype does not appear to be possible due to the development
of an anti-viral immune response. Nine clinical trials have
evaluated non-viral gene transfer
to the upper and lower airways of CF patients [50]. For the most
part these were proof of principle and Phase I safety studies. None
of the trials were designed to assess clinical efficacy. A recent
review article provides detailed informa- tion about these clinical
trials, what vectors were used and their drawbacks [45].
Figure 4 Gamma camera images of four adult patients with cystic
fibrosis and different FEV1 values showing distribution of an
aerosol containing the radioisotope 99mtechnetium. Uniform
deposition of aerosolized radioisotope is reduced in patients with
low FEV1 and severe obstruction (from Reference [15] with
Permission).
Recent developments in the UK hold new promise for improving CF
lung disease through gene therapy [45]. The UK CF Gene Therapy
Consortium (http: www.cfgenetherapy.org.uk) is currently conducting
the only active CF gene therapy clinical trial. This will be a
multi-dose clinical trial using the non-viral cationic lipid
formulation GL67A (Genzyme, Cambridge, MA, USA) with certain
modifications, including CpG-depletion and the incorporation of an
hCEFI promoter called pGM169 [45]. CpG-free plasmids reduce
inflammation and lead to long- acting gene expression when
administered to the mouse lung [45,53]. The hCEFI promoter also
prolongs gene expression in mice [53]. A safe dose for a multi-dose
double-blinded placebo-controlled trial of this new for- mulation
has been determined and trial participants have been recruited
[54]. Participants will be treated with 12 monthly doses delivered
by the AeroEclipseII Breath-Actuated Nebulizer (Trudell Medical
Instruments, London, Canada) over a year period [55].
Future directions Successful correction of lung diseases with
inhaled gene therapy remains elusive. A number of challenges must
be overcome before pulmonary gene therapy becomes a reality. These
include: (1) developing gene vectors that can more efficiently
penetrate the mucus barrier and cell membrane, navigate the cell
cytoplasm and transfer DNA material to the cell nucleus; (2)
improving delivery of gene vectors to infants; and (3) developing
formula- tions that are safe and effective for acute and chronic
administrations.
Vaccination by inhalation The rationale for aerosolized vaccination
is based on the following advantages over injection therapy,
particularly in developing countries. First, vaccination by
inhalation
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avoids the need for disposal strategies for the large num- ber of
needles that are used in mass campaigns in devel- oping countries.
Secondly, it prevents the spread of blood borne diseases such as
hepatitis B and HIV, which can be transmitted by improper use and
handling of used sharps. Thirdly, administration of a vaccine via
the aerosol route has less need for medical personnel, or a medical
setting, compared to administration by injection, and should
facilitate vaccination implementation in developing countries.
Another rationale for aerosolized vaccin- ation is that it induces
protection by exposure of the airway mucosa to agents that directly
affect the lungs and cause diseases such as tuberculosis,
diphtheria, pneumococcal pneumonia, measles, mumps and ru- bella.
Airway mucosal vaccination may also represent a potential approach
for immunizing against agents that do not directly affect the lungs
such as human papil- loma virus, or hepatitis B virus, by inducing
relevant antibodies in the serum. Because of the advantages to
aerosolized immunization,
a number of vaccines are being tested for feasibility and efficacy
via the pulmonary route. Many of these are still in preclinical
stages and have not progressed to clinical trials. Brief
descriptions of results from these early studies are described
here. Hepatitis B virus infection remains an im- portant global
health concern despite effective vaccines that are available by
injection. But, for reasons mentioned above, injection therapy for
hepatitis B is restricted in the developing world. Although
inhalation therapy is of inter- est, it is unknown if immunization
is possible by inhalation of hepatitis vaccine. A few animal
studies have begun to investigate the effects of particle size and
formulation on this route of administration. A liquid suspension of
hepatitis B vaccine PLGA (poly-D,L-lactide-co-glycolide) or PLA
(poly-lactic acid), nanoparticles of different sizes administered
to rats using a Microsprayer® (Penn-Century, Inc., Wyndmoor, PA,
USA) resulted in humoral and mu- cosal immune responses that varied
with particle size and hydrophobicity of the polymers used [56]. A
dry powder of hepatitis B vaccine nanoparticles administered by the
Insufflator® (Penn-Century, Inc.) led to lower IgG and higher IgA
in guinea pigs, compared to intramuscular injection [57]. A liquid
suspension of PLGA microspheres of hepatitis B vaccine,
administered by Microsprayer®, showed that immunogenicity in rats
was a function of par- ticle size [58]. Safety and tolerance of
intranasal administration of hepa-
titis B vaccine (NASVAC), comprised of hepatitis B virus (HBV)
surface (HBsAg) and core antigens (HBcAg), with Accuspray® (Becton
Dickinson and Company, Franklin Lakes NJ, USA) has been
demonstrated in a small group of healthy volunteers [59]. However,
large, randomized con- trolled clinical trials with this inhaled
hepatitis B vaccine are needed to show efficacy.
Administration of diphtheria vaccine by inhalation is of interest
because it would avoid the high probability of a local reaction
that occurs at the site of vaccination with intramuscular
injection. It would be a safer route of ad- ministration in
developing countries and might induce mucosal IgA antibody which
could bind to the exotoxin released by Cornyebacterium diphtheriae,
preventing it from entering and colonizing the airway mucosal mem-
brane [60]. Inhaled diphtheria vaccine is in early stages of
development, but a dry powder formulation of diphtheria CRM-197
antigen with PLGA as an adjuvant, adminis- tered using the
Insufflator®, resulted in lower IgG in the sera and higher IgA in
the BAL of guinea pigs, compared to intramuscular injection [60].
The urgency to address drug-resistant TB has led to a
resurgence in interest in inhalation as a route of adminis- tration
for anti-TB drugs to treat TB as well as vaccines to prevent TB. A
recent review of the status of anti-TB drugs is provided by Hickey
et al. [61]. Small clinical trials suggest that immunotherapy with
inhaled interferon- gamma [62], or inhalation of a dry powder
formulation of the antibiotic capreomycin with a hand-held inhaler
(Cyclohaler®, Plastiape, Italy), might be beneficial to TB pa-
tients [63]. However, large, randomized controlled clinical trials
are needed to further evaluate efficacy and safety. Mucosal
immunity for protection against TB has
been theorized, but is yet unproven in clinical trials.
Nevertheless, a number of novel formulations including
nanoparticles and dry powders of antigen/adjuvant com- binations
are being evaluated in animal models [64]. Two examples are
provided here. A suspension of nanoparti- cles (i.e. particles
<0.1 μm in diameter) conjugated with Ag85B tuberculosis antigen
and delivered through the nostrils of mice showed better protection
against subse- quent challenge, compared to intradermal delivery
[65]. A dry powder of live- attenuated tuberculosis vaccine bacille
Calmette-Guerin (BCG), administered by an Insufflator®, resulted in
a significantly reduced bacterial burden and lung pathology in
guinea pigs subsequently challenged with virulent Mycobacterium
tuberculosis, compared to untreated animals and control animals im-
munized with the standard parenteral BCG [66]. Further
investigation is needed to bring these products forward.
Immunization against the human papilloma virus by in-
halation has been tested in a small clinical trial by Nardelli-
Haefliger and colleagues [67]. This was a dose escalation study of
intranasal and oral inhalation of a human papil- loma virus-like
particle (HPV16 VLP) vaccine aerosol. Nasal administration was via
a Devilbiss® nebulizer sprayed into each nostril. Pulmonary
administration was achieved using a sonication-type nebulizer and
mouthpiece. Healthy adult female volunteers inhaled two doses of
the vaccine on day 0 and day 2 by nose, or mouth. Doses escalated
from 2 μg to 50 μg and 250 μg. Volunteers who inhaled
Laube Translational Respiratory Medicine 2014, 2:3 Page 8 of 12
http://www.transrespmed.com/content/2/1/3
250 μg by mouth seroconverted (an indicator of vaccin- ation) and
the magnitude of their serum IgG and IgA responses was similar to
that seen with an historically- treated group that was administered
50 μg by intramuscular injection. Lower doses by oral inhalation
were less effective and intranasal vaccination was poorly
immunogenic for most volunteers. These data raise the possibility
that ad- ministration of the VLP vaccine via oral inhalation may
offer an alternative to systemic immunization. More trials are
needed to confirm that aerosol vaccination is safe, im- munogenic
and protective against genital HPV infection. Gordon et al. [68]
compared the effect of intramuscular
vs. inhaled 23-valent pneumococcal capsular polysaccharide vaccine
(23-PPV) on pulmonary mucosal immunoglobulin levels. Vaccine was
delivered by jet nebulizer (Sidestream®, Respironics, Murrysville,
PA, USA). Bronchoalveolar lavage (BAL) and serum were collected
from 33 adults before and 1 month after injected (n=16) or inhaled
(n=17) 23-PPV. Levels of pneumococcal capsule-specific IgG and IgA
to types 1, 9V and 14 were measured in each sample. Injected 23-PPV
produced a significant increase in types 1, 9V and 14
capsule-specific IgG and type 1 IgA in both serum and BAL. Inhaled
vaccine produced no response in either BAL or serum.
Best example of vaccination by inhalation: preventing measles with
inhaled measles vaccine Inhaled measles vaccine is furthest along
in drug develop- ment, compared to the other inhaled vaccine
candidates mentioned above and is, therefore, the best example of
vaccination by inhalation. Its development has also been greatly
influenced by lessons learned from the Exubera® inhaled insulin
experience. The worldwide incidence of measles has been declining
for the last ten years. However, populations in some countries
remain unprotected. For example, an estimated 20 million children
worldwide were under-vaccinated in 2012 [69]. If infants are not
ad- equately immunized against measles, the entire com- munity will
be at risk for measles epidemics. Over three decades ago, Dr.
Albert Sabin and colleagues
proved the feasibility of vaccination by aerosolized measles
vaccine [70,71]. Since then, other trials have demonstrated that
measles vaccine administered by aerosol provides a superior
boosting response compared to vaccination by injection in
school-age children [72,73]. However, studies performed in infants
younger than 10 months of age showed that seroconversion rates were
lower with aerosolized than subcutaneous vaccine [74]. This may
have been due to an inadequate dose delivered to the lungs of these
infants, since an inefficient nebulizer and face mask was used in
those trials. Thus, a major challenge to developing an aerosolized
vaccine for pre- venting measles in the developing world is to
deliver an adequate dose to infants.
A second challenge to the development of an inhalable measles
vaccine is the need for new delivery devices. Such delivery devices
need to be efficient, portable and battery operated, since
electricity is not readily available in villages in developing
countries. New, efficient, port- able devices that are
battery-operated are now available for liquid aerosol deliver (i.e.
vibrating mesh devices) and for dry powder delivery. Details about
how these devices operate and their proper use can be found else-
where [5]. However, it is only within the last 4–5 years that these
devices have been incorporated into clinical trials that are
testing the efficacy of inhalable measles vaccine. Unfortunately,
many of these trials have only recently been completed, or are
being completed, and results are not yet published. An update of
the status of those trials, the formulation of measles vaccine
being tested and the devices that are being used to deliver the
vaccine is provided below. In the early 2000s, the World Health
Organization
(WHO) began work on an aerosolized measles vaccine that could be
used in mass immunization campaigns in developing countries. The
WHO decided to aerosolize the liquid formulation that was licensed
for injection therapy and had proven effective by inhalation in
earlier studies in Mexico [70,71]. This was the Edmonston- Zagreb
(EZ) live-attenuated measles vaccine. This choice meant that the
WHO did not have to reformulate the vaccine, which could have
resulted in years of additional testing. After several years of
device development in col- laboration with the U.S. CDC, the Bill
and Melinda Gates Foundation and Aerogen (Galway, Ireland), the WHO
began testing the Aerogen AeronebGo® delivery system in India. This
is a portable, battery-operated vibrating mesh device with a face
mask for infant aerosol delivery (Figure 5). A Phase III trial in
2,000 children <12 months old was recently completed. Data are
being analyzed and results will be compared to those obtained with
subcuta- neous (SC) administration of measles vaccine in a similar
age-group. The possibility of delivering a combination aerosol
vac-
cine to protect against measles, mumps and rubella with the
AeronebGo® device has also being conducted [75]. This was an
exploratory study to evaluate the safety and antibody responses to
each component of MMR II (Attenuvax measles live-attenuated
vaccine, Jeryl Lynn mumps live-attenuated vaccine and L-Zagreb
mumps live- attenuated vaccine) in healthy adults 21–38 years of
age. The investigators chose to use the AeronebGo® device be- cause
previous studies with aerosolized Schwarz measles vaccine (similar
to the Attenuvax base sequence) showed rapid degradation of vaccine
potency using a jet nebulizer and compressed air system. Results
from the more recent study showed that aerosolization of the three
components of MMRII vaccine was safe and produced secondary
Figure 5 The Aerogen Aeroneb Go® delivery system (Aerogen, Galway
Ireland) is being developed to deliver liquid measles vaccine to
children and infants in developing countries. The device consists
of a medication chamber that is located in the upper part of a
plastic holder. The outlet port extends from the holder and can be
fitted with a mouthpiece or facemask. A vibrating membrane, the
generator OnQ®, pumps fluid through small holes generating aerosol
with a median diameter of 3.6 microns. The control module works
with three AA batteries and is connected to the medication chamber
through a removable cord [75]. (Image downloaded from Aerogen
website at http:www.aerogen. com/aeroneb-go.html).
Figure 6 The PuffHaler® (Aktiv-Dry, LLC, Boulder, CO, USA) (A) and
th USA) (B) are two new devices that are being developed to deliver
me developing countries. When the PuffHaler squeeze bulb is
compressed, the through the powder in an aluminum foil blister and
the aerosol cloud fills a c affixed to a facemask from which the
subject breathes for 30 s to become va pressurize the capsule
containing the powder vaccine. As the pressure rises, t captured in
the disposable spacer for delivery through a silicone facemask
(So
Laube Translational Respiratory Medicine 2014, 2:3 Page 9 of 12
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immune responses in healthy adults. Similar safety studies need to
be performed in children. Within the last 6–8 years, the WHO, the
U.S. CDC,
the Bill and Melinda Gates Foundation, the NIH and Aktiv-Dry, LLC
(Boulder, CO, USA) began working on a powder formulation of the EZ
live-attenuated measles vaccine. The advantage to a powder
formulation is that it does not need refrigeration, which is also
often lacking at sites of mass campaigns in developing countries.
The powder was developed by Aktiv-Dry, LLC. The two de- vices to
deliver the powder are called the PuffHaler® and the Solovent® and
are shown in Figure 6A and 6B. They were developed by Aktiv-Dry and
BD Technologies (Becton, Dickinson and Company), respectively. Both
devices incorporate a holding chamber that allows the powder to be
actuated and held in place until inhalation is initiated. Such a
holding chamber for a powder aerosol was first introduced in the
Exubera® Pulmonary Insulin Delivery System that was used to
administer insulin aero- sol. Unlike the Exubera device, these
devices are con- structed of inexpensive materials such that the
cost of delivering dry powder measles vaccine will not cost more
than intramuscular injection administration. Both devices also
include flexible face masks for infant delivery. In a recent
pre-clinical trial, dry powder vaccine delivered by these two
devices provided full protection against mea- sles infection in
Rhesus macaques [76]. A large clinical trial to test the efficacy
of this powder formulation in humans is currently being planned.
Unlike aerosol applications for systemic drug delivery
and gene therapy, immunization by inhalation does not re- quire
chronic repeat dosing for efficacy. For many vaccines, immunization
may be achieved with 1–2 aerosol treat- ments followed by a booster
treatment. Thus, there is less concern about the safety of repeated
lung dosing with
e Solovent® (Becton, Dickinson and Company, Franklin Lakes, NJ,
asles vaccine as a dry powder to children and infants in silicone
rubber burst-valve pops open. The air rushes into the disperser
ollapsed plastic bag reservoir. The aerosol-filled bag is detached
and ccinated (Puff-mask). The syringe of the BD Solovent device is
used to he thin films sealing the capsule rupture, and the powder
is expelled and l-mask) (from Reference [76] with
Permission).
immunization by inhalation, compared to systemic drug delivery and
gene therapy by inhalation. Nevertheless, safety remains an issue
with inhaled vaccines because some patient populations (e.g.
patients with allergic asthma) may be more sensitive to excipients
in the formulations and care-givers who are immunosuppressed may be
more vulnerable to vaccine exposure than non-immunosuppressed
individuals.
Future directions Vaccination by inhalation is a promising new
method for immunization. It has already been used in large
populations and appears to be a feasible method for mass
vaccinations. Recent developments in device innovation have made
reliable, portable aerosol dosing in mass campaigns pos- sible.
Improvements in delivery to infants and in the development of
vaccines that do not require refrigeration (i.e. powders) and are
stable at the ambient temperatures of the tropics could make this
the preferred route of administration for a number of vaccines in
the future.
Conclusions The role of aerosol therapy has changed over the years
to now include systemic drug delivery by inhalation, inhaled gene
therapy and vaccination by inhalation. Each of these new
applications has led to the development of new deliv- ery devices
and achieved varying degrees of success in treat- ing their disease
targets. The continued expansion of the role of aerosol therapy in
the future will depend on: (1) improving the bioavailability of
systemically delivered drugs; (2) developing gene therapy vectors
that can efficiently penetrate the airway mucus barrier and cell
membrane, navigate the cell cytoplasm and efficiently transfer DNA
material to the cell nucleus; (3) improving delivery of gene
vectors and vaccines to infants; and (4) developing formula- tions
that are safe for acute and chronic administrations.
Competing interests The author declares that she has no competing
interests. Nevertheless, she was paid $1988.00 for her recent
speaking engagement at the International Society for Respiratory
Diseases in Shanghai, China November 8-10, 2013, where she
presented information found in this article in slide format.
Received: 17 September 2013 Accepted: 23 October 2013 Published: 13
January 2014
References 1. Global Initiative for Asthma (GINA), National Heart
Lung and Blood Institute,
National Institutes of Health: GINA report. Global strategy for
asthma management and prevention. Bethesda: National Institutes of
Health; 2006.
2. Global Initiative for Obstructive Lung Disease (GOLD), National
Heart Lung and Blood Institute, National Institutes of Health: GOLD
report. Global strategy for diagnosis, management and prevention of
COPD. Bethesda: National Institutes of Health; 2009.
3. Flume PA, O’Sullivan BP, Robinson KA, Goss CH, Mogayzel PJ Jr,
Willey-Courand DB, Bujan J, Finder J, Lester M, Quittell L,
Rosenblatt R, Vender RL, Hazle L, Sabadosa K, Marshall B: Cystic
fibrosis pulmonary guidelines: chronic medications for maintenance
of lung health. Am J Respir Crit Care Med 2007, 176:957–969.
4. Heijerman H, Westerman E, Conway S, Touw D, Döring G, consensus
working group: Inhaled medication and inhalation devices for lung
disease in patients with cystic fibrosis: a European consensus. J
Cyst Fibros 2009, 8:295–315.
5. Laube BL, Janssens HM, de Jongh FH, Devadason SG, Dhand R, Diot
P, Everard ML, Horvath I, Navalesi P, Voshaar T, Chrystyn H: What
the pulmonary specialist should know about the new inhalation
therapies. Eur Respir J 2011, 37:1308–1331.
6. Carter NJ, Curran MP: Live attenuated influenza vaccine
(FluMist®; Fluenz™): a review of its use in the prevention of
seasonal influenza in children and adults. Drugs 2011,
71:1591–1622.
7. Drugs for postmenopausal osteoporosis. Treat Guidel Med Lett
2008, 6:67–74.
8. Vestergaard P, Mosekilde L, Langdahl B: Fracture prevention in
postmenopausal women. Clin Evid 2011, 05:1109.
9. Pillow JJ, Minocchieri S: Innovation in surfactant therapy II:
surfactant administration by aerosolization. Neonatology 2012,
101:337–344.
10. Möller W, Lübbers C, Münzing W, Canis M: Pulsating airflow and
drug delivery to paranasal sinuses. Curr Opin Otolaryngol Head Neck
Surg 2011, 19:48–53.
11. Durand M, Le Guellec S, Pourchez J, Dubois F, Aubert G,
Chantrel G, Vecellio L, Hupin C, De Gersem R, Reychler G, Pitance
L, Diot P, Jamar F: Sonic aerosol therapy to target maxillary
sinuses. Eur Ann Otorhinolaryngol Head Neck Dis 2012,
129:244–250.
12. Silberstein SD, Kori SH: Dihydroergotamine: a review of
formulation approaches for the acute treatment of migraine. CNS
Drugs 2013, 27:385–394.
13. Carr WW: New therapeutic options for allergic rhinitis: back to
the future with intranasal corticosteroid aerosols. Am J Rhinol
Allergy 2013, 27:309–313.
14. Podolska K, Stachurska A, Hajdukiewicz K, Maecki M: Gene
therapy prospects–intranasal delivery of therapeutic genes. Adv
Clin Exp Med 2012, 21:525–534.
15. Laube BL: The expanding role of aerosols in systemic drug
delivery, gene therapy, and vaccination. Respir Care 2005,
50:1161–1174.
16. Alexander-Williams JM, Rowbotham DJ: Novel routes of opioid
administration. Br J Anaesth 1998, 81:3–7.
17. Thipphawong J, Babul N, Morishige R, Morishige RJ, Findlay HK,
Reber KR, Millward GJ, Otulana BA: Analgesic efficacy of inhaled
morphine in patients after bunionectomy surgery. Anesthesiology
2003, 99:693–700.
18. Aurora SK, Silberstein SD, Kori SH, Tepper SJ, Borland SW, Wang
M, Dodick DW: MAP0004, orally inhaled DHE: a randomized, controlled
study in the acute treatment of migraine. Headache 2011,
51:507–517.
19. International Diabetes Federation Diabetes Atlas: International
Diabetes Federation Diabetes Atlas. 5th edition.
http://www.idf.org/diabetesatlas/5e/ the-global-burden.
20. Wigley FM, Londono JH, Wood SH, Shipp JC, Waldman RH: Insulin
across respiratory mucosae by aerosol delivery. Diabetes 1971,
20:552–556.
21. Elliott RB, Edgar BW, Pilcher CC, Quested C, McMaster J:
Parenteral absorption of insulin from the lung in diabetic
children. Aust Paediatr J 1987, 23:293–297.
22. Adjei AL, Fu Lu M-Y: LH-RH Analogs. In Inhalation delivery of
therapeutic peptides and proteins. Edited by Adjei AL, Gupta PK.
New York: Marcel Dekker; 1997:389–412.
23. Laube BL, Georgopoulos A, Adams GK 3rd: Preliminary study of
the efficacy of insulin aerosol delivered by oral inhalation in
diabetic subjects. JAMA 1993, 269:2106–2109.
24. Laube BL, Benedict GW, Dobs AS: Time to peak insulin level,
relative bioavailability, and effect of site of deposition of
nebulized insulin in patients with noninsulin-dependent diabetes
mellitus. J Aerosol Med 1998, 11:153–173.
25. Cefalu WT, Skyler JS, Kourides IA, Landschulz WH, Balagtas CC,
Cheng S, Gelfand RA, Inhaled Insulin Study Group: Inhaled human
insulin treatment in patients with type 2 diabetes mellitus. Ann
Intern Med 2001, 134:203–207.
26. Skyler JS, Cefalu WT, Kourides IA, Landschulz WH, Balagtas CC,
Cheng SL, Gelfand RA: Efficacy of inhaled human insulin in type 1
diabetes mellitus: a randomized proof-of-concept study. Lancet
2001, 357:331–335.
27. Harper NJ, Gray S, de Groot J, Parker JM, Sadrzadeh N, Schuler
C, Schumacher JD, Seshadri S, Smith AE, Steeno GS, Stevenson CL,
Taniare R, Wang M, Bennett DB: The design and performance of the
Exubera®
Laube Translational Respiratory Medicine 2014, 2:3 Page 11 of 12
http://www.transrespmed.com/content/2/1/3
pulmonary insulin delivery system. Diabetes Technol Ther 2007,
9(Suppl 1):S16–S27.
28. Cefalu WT, Wang ZQ: Clinical research obsevations with use of
Exubera® in patients with type 1 and type 2 diabetes. Diabetes
Technol Ther 2007, 9(Suppl 1):S28–S40.
29. Wollmer P, Pieber TR, Gall M-A, Brunton S: Delivering
needle-free insulin using the AERx® IDMS (insulin diabetes
management system) technology. Diabetes Techol Ther 2007, 9(Suppl
1):S57–S64.
30. Muchmore DB, Silverman B, de la Pena A, Tobian J: The Air®
inhaled insulin system: system components and
pharmacokinetic/glucodynamic data. Diabetes Technol Ther 2007,
9(Suppl 1):S41–S47.
31. Ellis SL, Gemperline KA, Garg S: Review of phase 2 studies
utilizing the Air® particle technology in the delivery of human
insulin inhalation powder versus subcutaneous regular or lispro
insulin in subjects with type 1 or type 2 diabetes. Diabetes
Technol Ther 2007, 9(Suppl 1):S48–S56.
32. Wall Street Journal On-Line http://online.wsj.com/article/
SB119269071993163273.html.
33. Skyler JS, Jovanovic L, Klioze S, Reis J, Duggan W, Inhaled
Human Insulin Type 1 Diabetes Study Group: Two-year safety and
efficacy of inhaled human insulin (Exubera) in adult patients with
type 1 diabetes. Diabetes Care 2007, 30:579–585.
34. MannKind Corporation.
http://www.mannkindcorp.com/product-pipeline-
diabetes-afrezza.htm.
35. Rosenstock J, Bergenstal R, DeFronzo RA, Hirsch IB, Klonoff D,
Boss AH, Kramer D, Petrucci R, Yu W, Levy B, for the 0008 Study
Group: Efficacy and safety of technosphere inhaled insulin compared
with technosphere powder placebo in insulin-naïve type 2 diabetes
suboptimally contolled with oral agents. Diabetes Care 2008,
31:2177–2182.
36. Rosenstock J, Lorber DL, Gnudi L, Howard CP, Bilheimer DW,
Chang PC, Petrucci RE, Boss AH, Richardson PC: Prandial inhaled
insulin plus basal insulin glargine versus twice daily biaspart
insulin for type 2 diabetes: a multicentre randomised trial. Lancet
2010, 375:2244–2253.
37. Neumiller JJ, Campbell RK, Wood LD: A review of inhaled
technosphere insulin. Ann Pharmacother 2010, 44:1231–1239.
38. Codrons V, Vanderbist F, Ucakar B, Preat V, Vanbever R: Impact
of formulation and methods of pulmonary delivery on absorption of
parathyroid hormone (1–34) from rat lungs. J Pharm Sci 2004,
93:1241–1252.
39. Bosquillon C, Preat V, Vanbever R: Pulmonary delivery of growth
hormone using dry powders and visualization of its local fate in
rats. J Control Release 2004, 96:233–244.
40. Todo H, Okamoto H, Iida K, Danjo K: Effect of additives on
insulin absorption from intratracheally administered dry powders in
rats. Int J Pharm 2001, 220:101–110.
41. Sakagami M, Sakon K, Kinoshita W, Makino Y: Enhanced pulmonary
absorption following aerosol administration of mucoadhesive powder
microspheres. J Control Release 2001, 77:117–129.
42. Seow Y, Wood MJ: Biological gene delivery vehicles: Beyond
viral vectors. Mol Ther 2009, 17:767–777.
43. Mali S: Delivery systems for gene therapy. Indian J Hum Genet
2013, 19:3–8. 44. Pichon C, Billiet L, Midoux P: Chemical vectors
for gene delivery:
uptake and intracellular trafficking. Curr Opin Biotechnol 2010,
21:640–645.
45. Griesenbach U, Alton EW: Expert opinion in biological therapy:
update on developments in lung gene transfer. Expert Opin Biol Ther
2013, 13:345–360.
46. Virella-Lowell I, Zusman B, Foust K, Loiler S, Conlon T, Song
S, Chesnut KA, Ferkol T, Flotte TR: Enhancing rAAV vector
expression in the lung. J Gene Med 2005, 7:842–850.
47. Sirninger J, Muller C, Braag S, Tang Q, Yue H, Detrisac C,
Ferkol T, Guggino WB, Flotte TR: Functional characterization of a
recombinant adeno-associated virus 5-pseudotyped cystic fibrosis
transmembrane conductance regulator vector. Hum Gene Ther 2004,
15:832–841.
48. Griesenbach U, Alton EW: Progress in gene and cell therapy for
cystic fibrosis lung disease. Curr Pharm Des 2012,
18:642–662.
49. Cystic Fibrosis Foundation Patient Registry Annual Data Report
to the Center Directors. Bethesda, Maryland: Cystic Fibrosis
Foundation; 2011. http://www.
cff.org/UploadedFiles/Research/ClinicalResearch/2011-Patient-Registry.pdf.
50. Griesenbach U, Alton EW: Gene transfer to the lung: lessons
learned from more than 2 decades of CF gene therapy. Adv Drug Deliv
Rev 2009, 61:128–139.
51. Moss RB, Rodman D, Spencer LT, Aitken ML, Zeitlin PL, Waltz D,
Milla C, Brody AS, Clancy JP, Ramsey B, Hamblett N, Heald AE:
Repeated adeno-associated virus serotype 2 aerosol-mediated cystic
fibrosis transmembrane regulator gene transfer to the lungs of
patients with cystic fibrosis: a multicenter, double-blind,
placebo-controlled trial. Chest 2004, 125:509–521.
52. Moss RB, Milla C, Colombo J, Accurso F, Zeitlin PL, Clancy JP,
Spencer LT, Pilewski J, Waltz DA, Dorkin HL, Ferkol T, Pian M,
Ramsey B, Carter BJ, Martin DB, Heald AE: Repeated aerosolized
AAV-CFTR for treatment of cystic fibrosis: a randomized
placebo-controlled phase 2B trial. Hum Gene Ther 2007,
18:726–732.
53. Hyde SC, Pringle IA, Abdullah S, Lawton AE, Davies LA,
Varathalingam A, Nunez-Alonso G, Green AM, Bazzani RP, Sumner-Jones
SG, Chan M, Li H, Yew NS, Cheng SH, Boyd AC, Davies JC, Griesenbach
U, Porteous DJ, Sheppard DN, Munkonge FM, Alton EW, Gill DR:
CpG-free plasmids confer reduced inflammation and sustained
pulmonary gene expression. Nat Biotechnol 2008, 26:549–551.
54. Alton EW, Boyd AC, Cheng SH, Cunningham S, Davies JC, Gill DR,
Griesenbach U, Higgins T, Hyde SC, Innes JA, Murray GD, Porteous
DJ: A randomised, double-blind, placebo-controlled phase IIB
clinical trial of repeated application of gene therapy in patients
with cystic fibrosis. Thorax. doi:10.1136/thoraxjnl-2013-203309.
Epub ahead of print.
55. Griesenbach U, Alton EW: Moving forward: cystic fibrosis gene
therapy. Hum Mol Genet 2013, 22(R1):R52–R58.
56. Thomas C, Rawat A, Hope-Weeks L, Ahsan F: Aerosolized PLA and
PLGA nanoparticles enhance humoral, mucosal and cytokine responses
to hepatitis B vaccine. Mol Pharm 2011, 8:405–415.
57. Muttil P, Prego C, Garcia-Contreras L, Pulliam B, Fallon JK,
Wang C, Hickey AJ, Edwards D: Immunization of guinea pigs with
novel hepatitis B antigen as nanoparticle aggregate powders
administered by the pulmonary route. AAPS J 2010, 12:330–337.
58. Thomas C, Gupta V, Ahsan F: Particle size influences the immune
response produced by hepatitis B vaccine formulated in inhalable
particles. Pharm Res 2010, 27:905–919.
59. Betancourt AA, Delgado CA, Estévez ZC, Martínez JC, Ríos GV,
Aureoles-Roselló SR, Zaldívar RA, Guzmán MA, Baile NF, Reyes PA,
Ruano LO, Fernández AC, Lobaina-Matos Y, Fernández AD, Madrazo AI,
Martínez MI, Baños ML, Alvarez NP, Baldo MD, Mestre RE, Pérez MV,
Martínez ME, Escobar DA, Guanche MJ, Cáceres LM, Betancourt RS,
Rando EH, Nieto GE, González VL, Rubido JC: Phase I clinical trial
in healthy adults of a nasal vaccine candidate containing
recombinant hepatitis B surface and core antigens. Int J Infect Dis
2007, 11:394–401.
60. Muttil P, Pulliam B, Garcia-Contreras L, Fallon JK, Wang C,
Hickey AJ, Edwards DA: Pulmonary immunization of guinea pigs with
diphtheria CRM-197 antigen as nanoparticle aggregate dry powders
enhance local and systemic immune responses. AAPS J 2010,
12:699–707.
61. Hickey AJ, Misra A, Fourie PB: Dry Powder Antibiotic Aerosol
Product Development: Inhaled Therapy for Tuberculosis. J Pharm Sci
2013, 102:3900–3907.
62. Gao X-F, Yang Z-W, Li J: Adjunctive therapy with
interferon-gamma for the treatment of pulmonary tuberculosis: a
systematic review. Int J Infect Dis 2011, 15:e594–e600.
63. Dharmadhikari AS, Kabadi M, Gerety B, Hickey AJ, Fourie PB,
Nardell E: Phase I, single-dose, resistant tuberculosis. Antimicrob
Agents Chemother 2013, 57:2613–2619.
64. Garcia-Contreras L, Awashthi S, Hanif SNM, Hickey AJ: Inhaled
vaccines for the prevention of tuberculosis. J Mycobac Dis 2012,
S1:002.
65. Ballester M, Nembrini C, Dhar N, de Titta A, de Piano C,
Pasquier M, Simeoni E, van der Vlies AJ, McKinney JD, Hubbell JA,
Swartz MA: Nanoparticle conjugation and pulmonary delivery enhance
the protective efficacy of Ag85B and CpG against tuberculosis.
Vaccine 2011, 29:6959–6966.
66. Garcia-Contreras L, Wong YL, Muttil P, Padilla D, Sadoff J,
Derousse J, Germishuizen WA, Goonesekera S, Elbert K, Bloom BR,
Miller R, Fourie PB, Hickey A, Edwards D: Immunization by a
bacterial aerosol. Proc Natl Acad Sci USA 2008,
105:4656–4660.
67. Nardelli-Haefliger D, Lurati F, Wirthner D, Spertini F,
Schiller JT, Lowy DR, Ponci F, De Grandi P: Immune responses
induced by lower airway mucosal immunisation with a human
papillomavirus type 16 virus-like particle vaccine. Vaccine 2005,
23:3634–3641.
68. Gordon SB, Malamba R, Mthunthama N, Jarman ER, Jambo K, Jere K,
Zijlstra EE, Molyneux ME, Dennis J, French N: Inhaled delivery of
23-valent
pneumococcal polysaccharide vaccine does not result in enhanced
pulmonary mucosal immunoglobulin responses. Vaccine 2008,
26:5400–5406.
69. Centers for Disease Control and Prevention.
http://www.cdc.gov/globalhealth/ measles/challenges/.
70. Sabin AB, Flores AA, de Castro JF, Sever JL, Madden DL,
Shekarchi I, Albrecht P: Successful immunization of children with
and without maternal antibody by aerosolized measles vaccine. I.
Different results with human diploid cell and chick embryo
fibroblast vaccines. JAMA 1983, 249:2651–2662.
71. Sabin AB, Flores AA, de Castro JF, Albrecht P, Sever JL,
Shekarchi I: Successful immunization of infants with and without
maternal antibody by aerosolized measles vaccine. II. Vaccine
comparisons and evidence for multiple antibody response. JAMA 1984,
251:2363–2371.
72. Bennett JV, de Castro JF, Valdespino-Gomez JL, Garcia-Garcia
ML, Islas-Romero R, Echaniz-Aviles G, Jimenez-Corona A,
Sepulveda-Amor J: Aerosolized measles and measles-rubella vaccines
induce better measles antibody booster responses than injected
vaccines: randomized trials in Mexican school children. Bull World
Health Organ 2002, 80:806–812.
73. Dilraj A, Cutts FT, de Castro JF, Wheeler JG, Brown D, Roth C,
Coovadia HM, Bennett JV: Response to different measles vaccine
strains given by aerosol and subcutaneous routes to school
children: a randomized trial. Lancet 2000, 355:798–803.
74. Low N, Kraemer S, Schneider M, Restrepo AMH: Immunogenicity and
safety of aerosolized measles vaccine: Systematic review and
meta-analysis. Vaccine 2008, 26:383–398.
75. Diaz-Ortega J-L, Bennett JV, Castaneda D, Arellano DM, Martinez
D, de Castro Fernandez J: Safety and antibody responses to
aerosolized MMR II vaccine in adults: An exploratory study. World
Journal of Vaccines 2012, 2:55–60.
76. Lin WH, Griffin DE, Rota PA, Papania M, Cape SP, Bennett D,
Quinn B, Sievers RE, Shermer C, Powell K, Adams RJ, Godin S,
Winston S: Successful respiratory immunization with dry powder
live-attenuated measles virus vaccine in rhesus macaques. Proc Natl
Acad Sci USA 2011, 108:2987–2992.
doi:10.1186/2213-0802-2-3 Cite this article as: Laube: The
expanding role of aerosols in systemic drug delivery, gene therapy
and vaccination: an update. Translational Respiratory Medicine 2014
2:3.
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Systemic drug delivery by inhalation
Best example of systemic drug delivery by aerosolization: treating
diabetes with oral inhalation of insulin
What went wrong?
Future directions
Best example of aerosolized gene therapy: treating cystic fibrosis
(CF)
Future directions
Best example of vaccination by inhalation: preventing measles with
inhaled measles vaccine
Future directions